Feedstock Quality Research Articles

Sensitivity Analysis and Anaerobic Digestion Modeling: A Scoping Review

A growing awareness of global climate change has led to an increased interest in investigating renewable energy sources, such as the anaerobic digestion of biomass. This process utilizes a wide range of microbial communities to degrade biodegradable material in feedstock through a complex series of biochemical interactions. Anaerobic digestion exhibits nonlinear dynamics due to the complex and interacting biochemical processes involved. Due to its dynamic and nonlinear behavior, uncertain feedstock quality, and sensitivity to the process’s environmental conditions, anaerobic digestion is highly susceptible to instabilities. Therefore, in order to model and operate a biogas production unit effectively, it is necessary to understand which parameters are most influential on the model outputs. This also reduces the amount of estimation required. Through a scoping review, the present study analyzes the studies on the application of sensitivity analysis in anaerobic digestion modeling. Both local and global sensitivity analysis approaches were carried out using different mathematical models. The results indicate that anaerobic digestion model no.1 (ADM1) was the most commonly used model for analyzing sensitivity. Both local and global sensitivity analyses are widely employed to investigate the influence of key model parameters such as kinetic, stoichiometric, and mass transfer parameters on model outputs such as biogas production, methane concentration, pH, or economic viability of the plant.

Predictive models enhance feedstock quality of corn stover via air classification

Predictive models enhance feedstock quality of corn stover via air classification

A Study of Challenges and Techno-Economic Assessment of Biogas Plants

Abstract: A promising sustainable method for generating energy from municipal, industrial, and animal wastes is biogas. The development of biogas can be combined with plans to enhance sanitation, lessen indoor air pollution, and cut greenhouse gas emissions. In addition to providing a techno-economic feasibility analysis of biogas plants, this research intends to identify technical and non-technological constraints preventing the widespread use of biogas in India. Different waste, renewable energy, and urban regulations have an impact on the distribution of biogas. Therefore, specific obstacles to India's current rural and urban biogas systems were identified. The findings demonstrate that there are significant differences in the nature and significance of obstacles amongst biogas systems due to variations in technological maturity, feedstock quality and availability, supply chain, awareness level, and policy support. The developed excel model also provides a full perspective of the economic factors used to assess the viability of a biogas plant project. Users may assess numerous situations and decide on the best course of action for their investment in the biogas sector by using a comparison and analysis technique.

STRONG STAYGREEN inhibits DNA binding of PvNAP transcription factors during leaf senescence in switchgrass.

Fine tuning the progression of leaf senescence is important for plant fitness in nature, while the "staygreen" phenotype with delayed leaf senescence has been considered a valuable agronomic trait in crop genetic improvement. In this study, a switchgrass (Panicum virgatum L.) CCCH-type Zinc finger gene, Strong Staygreen (PvSSG), was characterized as a suppressor of leaf senescence as overexpression or suppression of the gene led to delayed or accelerated leaf senescence, respectively. Transcriptomic analysis marked that chlorophyll (Chl) catabolic pathway genes were involved in the PvSSG-regulated leaf senescence. PvSSG was identified as a nucleus-localized protein with no transcriptional activity. By yeast two-hybrid screening, we identified its interacting proteins, including a pair of paralogous transcription factors, PvNAP1/2 (NAC-LIKE, ACTIVATED BY AP3/PI). Overexpression of PvNAPs led to precocious leaf senescence at least partially by directly targeting and transactivating Chl catabolic genes to promote Chl degradation. PvSSG, through protein-protein interaction, repressed the DNA-binding efficiency of PvNAPs and alleviated its transactivating effect on downstream genes, thereby functioning as a "brake" in the progression of leaf senescence. Moreover, overexpression of PvSSG resulted in up to 47% higher biomass yield and improved biomass feedstock quality, reiterating the importance of leaf senescence regulation in the genetic improvement of switchgrass and other feedstock crops.

Advancing biomass pyrolysis by torrefaction pretreatment: Linking the productions of bio-oil and oxygenated chemicals to torrefaction severity

Torrefaction is an efficient pretreatment method to improve the quality of biomass feedstock and resulting bio-oil. Herein, the relationships of torrefaction severity of sweet sorghum bagasse (SSB) with its physicochemical properties and resulting pyrolytic product distributions were systemically investigated. The SSB was first pretreated by torrefaction at different temperatures (230, 260, and 290 °C) with a constant residence time of 30 min, and the resulting torrefied SSB was subsequently pyrolyzed at 500 °C for the production of bio-oil. The carbon enrichment index (CEI) is used as an indicator to quantitatively reflect the torrefaction severity of SSB. The results show that the extents of decarbonization, dehydrogenation, and deoxygenation reactions of SSB increase linearly with the increase of CEI, and the extent of deoxygenation reaction is the most severe among them. Torrefaction can effectively regulate the pyrolytic production distributions of SSB, and severe torrefaction favors the formation of biochar. The productions of bio-oil and major oxygenated chemicals (e.g., ketones, carboxylic acids, and phenols) in bio-oil as the functions of CEI could be fitted well by quadratic polynomial functions. The findings can guide the rational design and optimization of the torrefaction process for improved biomass pyrolysis.

Optimization and production of alpha-amylase using Bacillus subtilis from apple peel: Comparison with alternate feedstock

Degradable waste generated from food processing industries has immense potential for producing valuable products. Apples constitute among the most widely consumed fruits in the food processing industry, but their peels remain unutilized. We explored the possibility of using apple peel as feedstock for production of alpha-amylase- a commercially important enzyme with role in food industry and bio-ethanol production that is critical to support nutrition and energy security. The utilization of locally sourced apple peel as feedstock, optimization of the conditions for the production of alpha-amylase through solid-state fermentation and comparison with potato peel-another widely available feedstock option is done. The Bacillus subtilis BS1934 strain was identified as a promising strain that could produce alpha-amylase efficiently at 50 0C. The obtained values i.e., 17468 and 5229 U/L of alpha-amylase from apple and potato peel, respectively through solid state fermentation in eight days were considered as optimum. The enzyme titres were 3-fold higher with apple peel as compared to potato peel in the medium, indicating superior quality of apple peel feedstock as compared to potato for amylase production. The production of amylase using agro-industrial residues, as apple peel may emerge as a cost-effective alternative to amylase from microbial sources for industrial purpose.

Biomass suspension catalysed the generation of various alkyl esters from acid oil and virgin cottonseed oil

A substantial reduction in the cost of biodiesel production necessitates the identification of less expensive lipid-bearing substrates and a cost-effective process. The present study demonstrates the use of biomass suspension of Aspergillus sps. as a whole-cell catalyst for the generation of various alkyl esters from acid oil and cottonseed oil with different alcohols (methanol to decanol) as acyl acceptors. The yield of alkyl esters increased from methanol (79%) to pentanol (87%), followed by a decrease from hexanol (80%) to decanol (55%) in the case of acid oil. The extent of transesterification was significantly higher [P < 0.05] in case of acid oil, with most of the acyl acceptors as compared to cottonseed oil. The study reveals the potential use of biomass suspension of fungus as a catalyst and acid oil as an alternative, low-cost bearing, and quality feedstock for the generation of biodiesel for a diverse variety of industrial/commercial use.

Transient CFD study of wet burden charging on dynamic in-furnace phenomena in an ironmaking blast furnace: Impacts and remedies

Water content is a key parameter of feedstock quality for ironmaking blast furnaces (BFs). Wet burden may be used in BF practice occasionally, but the impacts of wet burden charging on in-furnace phenomena of BF are not yet clear, especially the transient BF performance after charging. In this study, a transient BF model is developed and used to quantify the transient in-furnace behaviours when various high moisture burden materials under different weather conditions are used. The effect of wet burden charging on the time evolution of in-furnace phenomena can be captured in terms of temperature fields, cohesive zone position, reduction degree and moisture distribution, as well as overall BF performance in terms of coke rate and top gas temperature. The results show that the coke rate is increased by 25% and the top gas temperature can be lower than 373 K (100 °C) within 1 h after charging wet burden of 4% water in ore and 10% water in coke. Then, the operation remedies in heavy rain weather are also studied and quantified. It is indicated that the decrease of oxygen enrichment to 0% in the blast and the reuse of dry burden for ~25 h can recover the BF performance by 73% and 91% in terms of top gas temperature, respectively. This model provides a cost-effective tool to study transient flow-thermal-chemical behaviours inside the BF when moisture burden is used in BFs.

Perspectives on strategies for improving ultra-deep desulfurization of liquid fuels through hydrotreatment: Catalyst improvement and feedstock pre-treatment

Reliance on crude oil remains high while the transition to green and renewable sources of fuel is still slow. Developing and strengthening strategies for reducing sulfur emissions from crude oil is therefore imperative and makes it possible to sustainably meet stringent regulatory sulfur level legislations in end-user liquid fuels (mostly less than 10 ppm). The burden of achieving these ultra-low sulfur levels has been passed to fuel refiners who are battling to achieve ultra-deep desulfurization through conventional hydroprocessing technologies. Removal of refractory sulfur-containing compounds has been cited as the main challenge due to several limitations with the current hydroprocessing catalysts. The inhibitory effects of nitrogen-containing compounds (especially the basic ones) is one of the major concerns. Several advances have been made to develop better strategies for achieving ultra-deep desulfurization and these include: improving hydroprocessing infrastructure, improving hydroprocessing catalysts, having additional steps for removing refractory sulfur-containing compounds and improving the quality of feedstocks. Herein, we provide perspectives that emphasize the importance of further developing hydroprocessing catalysts and pre-treating feedstocks to remove nitrogen-containing compounds prior to hydroprocessing as promising strategies for sustainably achieving ultra-deep hydroprocessing.

Multiscale Shear Properties and Flow Performance of Milled Woody Biomass

One dominant challenge facing the development of biorefineries is achieving consistent system throughput with highly variant biomass feedstock quality and handling performance. Current handling unit operations are adapted from other sectors (primarily agriculture), where some simplifying assumptions about granular mechanics and flow performance do not translate well to a highly compressible and anisotropic material with nonlinear time- and stress-dependent properties. This work explores the shear and frictional properties of loblolly pine at multiple experimental test apparatus and particle scales to elucidate a property window that defines the shear behavior over a range of material attributes (particle size, size distribution, moisture content, etc.). In general, it was observed that the bulk internal friction and apparent cohesion depend strongly on both the stress state of the sample in granular shear testers and the overall particle size and distribution span. For equipment designed to characterize the quasi-static shear stress failure of bulk materials ranging from 50 to 1,000 ml in test volume, similar test results were observed for finely milled particles (50% passing size of 1.4 mm) with a narrow size distribution (span between 10 and 90% passing size of 0.9 mm), while stress chaining and over-torque issues persisted for the bench-scale test apparatus for larger particle sizes or widely dispersed sample sizes. Measurement of the anisotropic particle–particle friction ranged from coefficients of approximately 0.20 to 0.45 and resulted in significantly higher and more variable friction measurements for larger particle sizes and in perpendicular alignment orientations. To supplement these laboratory-scale properties, this work explores the flow of loblolly pine and Douglas fir through a pilot-scale wedge-shaped hopper and a screw feeder. For the gravity-driven hopper flow, the critical arching distance and mass discharge rate ranged from approximately 10 to 30 mm and 2 to 16 tons/hour, respectively, for both materials, where the arching distance depends strongly on the overall particle size and depends less on the hopper inclination angle. Comparatively, the auger feeder was found to be much more impacted by the size of the particles, where smaller particles had a more consistent and stable flow while consuming less power.

Modeling quality of concentration factory feedstock in ferruginous quartzite mining at the Lebedinskoe deposit

Statistical modeling of daily average or mean-shift content of useful component in ore hauled from a certain production face to a rehandling point, to an intermediate (including blending) storage, or to a concentration factory enables mine planning to proceed to the next level. This also allows meeting one of the major tasks of the modern mining industry, namely, stabilization of the useful component content in processing feedstock. The geological information quality and initial interpretation are the major factors of data reliability in modeling any mineral mining, production or processing chain. Currently, almost all mining companies in Russia have introduced operational exploration procedures. The analysis of the long-term operational exploration data collectively with the geological exploration data allows determining patterns of useful component in different areas and sites of a mineral deposit. The present research made it possible to obtain magnetite content variation per levels of the test deposit and to reveal correlations between different quality characteristics. Using the statistics on magnetite distribution in the ferruginous quartzite ore body of the Lebedinskoe deposit, as well as with regard to the current capacities of production faces, the simulation model has been constructed in the framework of this research. The model enables prediction of the daily mean content of the useful component in the mineral feedstock of the concentration factory at different number of sampling points and at the varied daily average production capacity.

Operational Excellence in a Biogas Plant through Integration of Lean Six Sigma Methodology

Process optimization with Lean Six Sigma (LSS) has become more popular every day for years in almost every kind of industry. This integration has brought an even wider variety of possible application areas for industries and research institutes. Recently, the use of LSS for process optimization in biological fields has become more and more common. In this study, LSS methodology is used for process optimization in an industrial scale biogas plant in Hamburg, Germany. The methodology used includes all the DMAIC cycle and related tools. Hypothesis tests were used to calculate the p-value of each experiment for the LSS interpretation. Due to the experimental factors, one-way ANOVA and 1-sample Z-test were used to determine the p-values. By conducting hypothesis testing after the analysis phase of this study, it was found that particle size, freshness of the substrate, and the amount of sand content in the substrate had a significant effect on the desired amount of biogas produced with a p-value of less than 0.01. These root causes led to approaches that focused on high quality feedstock and sufficient pretreatment methods. This paper represents a pioneering example of integrating Lean Six Sigma into biogas plant operation.

Biomass Energy Resources: Feedstock Quality and Bioenergy Sustainability

The fossil fuel society is facing environmental, socio-economic, and geopolitical issues [...]

Spectroscopic analysis reveals that soil phosphorus availability and plant allocation strategies impact feedstock quality of nutrient-limited switchgrass

The perennial native switchgrass adapts better than other plant species do to marginal soils with low plant-available nutrients, including those with low phosphorus (P) content. Switchgrass roots and their associated microorganisms can alter the pools of available P throughout the whole soil profile making predictions of P availability in situ challenging. Plant P homeostasis makes monitoring of P limitation via measurements of plant P content alone difficult to interpret. To address these challenges, we developed a machine-learning model trained with high accuracy using the leaf tissue chemical profile, rather than P content. By applying this learned model in field trials across two sites with contrasting extractable soil P, we observed that actual plant available P in soil was more similar than expected, suggesting that adaptations occurred to alleviate the apparent P constraint. These adaptations come at a metabolic cost to the plant that have consequences for feedstock chemical components and quality. We observed that other biochemical signatures of P limitation, such as decreased cellulose-to-lignin ratios, were apparent, indicating re-allocation of carbon resources may have contributed to increased P acquisition. Plant P allocation strategies also differed across sites, and these differences were correlated with the subsequent year’s biomass yields.

A new model for predicting the flow properties of Ti-6Al-4V-MIM feedstocks

Titanium and its alloys have high specific strength and high resistance to corrosion but are expensive to manufacture. Manufacturing cost can be reduced by using metal injection moulding (MIM) to produce near-net shaped intricate parts. Feedstock rheology affects feedstock homogeneity, injection moulding and quality of the MIM parts. Methods to quickly obtain these rheological parameters will help optimise processing conditions and hence decrease manufacturing cost. Feedstocks were produced from hydride-dehydride titanium alloy powder and binder containing polyethylene glycol, polyvinyl butyral and stearic acid using a four-stage mixing process. Feedstock rheology and morphology were investigated using a capillary rheometer and a scanning electron microscope. A new model, which incorporates a newly defined parameter, feedstock flow index (p), was developed for predicting the rheological properties of titanium-based feedstocks using shear stress and melt flow rate. The MRF value, obtained from these low-cost rheological tests predicted HDH Ti-6Al-4V-MIM feedstock flow properties well.

Application of acidic ionic liquids for the treatment of acidic low grade palm oil for biodiesel production

Employing low quality feedstocks for biodiesel production can present cost reduction opportunities due to its wide availability and cost effectiveness. However, most low quality feedstocks have high free fatty acid (FFA) content which is not feasible for biodiesel production through direct transesterification due to soap formation. Thus, a pre-treatment step through FFA esterification could reduce the FFA content while simultaneously yielding fatty acid methyl esters (FAME). In this study, the catalytic activity of ten ionic liquids (ILs) were screened for the esterification of FFA in acidic crude palm oil (ACPO). 1‑butyl‑3-methylimidazolium hydrogen sulfate as IL exhibited the highest catalytic activity and was further investigated to determine the optimum operating parameters such as IL dosage, molar ratio, reaction temperature and time. Single factor optimization was employed for the laboratory scale batch esterification reaction. The FFA content was reduced from 10.77% to less than 1% using the following optimum conditions: 4% IL to oil, molar ratio of 10:1 (methanol to oil), 120 min reaction time and 60 °C reaction temperature. Under optimum conditions, the IL can be recycled five times with minimal loss in catalytic activity, highlighting its feasibility as an industrial catalyst for esterification of acidic oils and fats.

The production of hydroprocessed renewable diesel with a catalyst regenerated using supercritical carbon dioxide (SCCO2)

Hydroprocessed renewable diesel was produced using a hydro-treatment technology that is mainly dependent on the feedstock quality and catalyst performance. In this study, the regeneration of NiMo/γ-Al2O3 hydroprocessing catalyst was investigated with continuous and batch operations for the purpose of recovering waste catalyst and improving catalyst performance. Supercritical carbon dioxide and co-solvent were utilized to perform the regeneration process, and the process parameters were discussed. Furthermore, the regenerated catalyst was characterized using TGA, FTIR, BET, and XRD methods and compared to both fresh and spent catalysts. It was found that the optimal regeneration for catalyst could be obtained using a batch mode at the pressure of 76 bar and the temperature of 523 K with injecting 10 mL per period hexane co-solvent for 3 periods, resulting in 15.5% of mass removal rate. The regenerated catalyst possessed >97% conversion while the fresh one obtained >99%.

Opportunities and challenges for the application of post-consumer plastic waste pyrolysis oils as steam cracker feedstocks: To decontaminate or not to decontaminate?

Thermochemical recycling of plastic waste to base chemicals via pyrolysis followed by a minimal amount of upgrading and steam cracking is expected to be the dominant chemical recycling technology in the coming decade. However, there are substantial safety and operational risks when using plastic waste pyrolysis oils instead of conventional fossil-based feedstocks. This is due to the fact that plastic waste pyrolysis oils contain a vast amount of contaminants which are the main drivers for corrosion, fouling and downstream catalyst poisoning in industrial steam cracking plants. Contaminants are therefore crucial to evaluate the steam cracking feasibility of these alternative feedstocks. Indeed, current plastic waste pyrolysis oils exceed typical feedstock specifications for numerous known contaminants, e.g. nitrogen (∼1650 vs. 100ppm max.), oxygen (∼1250 vs. 100ppm max.), chlorine (∼1460vs. 3ppm max.), iron (∼33 vs. 0.001ppm max.), sodium (∼0.8 vs. 0.125ppm max.)and calcium (∼17vs. 0.5ppm max.). Pyrolysis oils produced from post-consumer plastic waste can only meet the current specifications set for industrial steam cracker feedstocks if they are upgraded, with hydrogen based technologies being the most effective, in combination with an effective pre-treatment of the plastic waste such as dehalogenation. Moreover, steam crackers are reliant on a stable and predictable feedstock quality and quantity representing a challenge with plastic waste being largely influenced by consumer behavior, seasonal changes and local sorting efficiencies. Nevertheless, with standardization of sorting plants this is expected to become less problematic in the coming decade.

Forest Bio-Hubs to Enhance Forest Health While Supporting the Emerging Bioeconomy—A Comparison between Three U.S. Regions

The emerging bioeconomy requires new supply chain paradigms for biomass materials to reach processing centers. Forest bio-hubs can be thought of as networks of collection points to facilitate biomass supply chains that feed from forest to central processing facilities. The design and functionality of forest bio-hubs depends on the form (e.g., vertically and horizontally integrated), and the quality and volume of feedstocks. In this paper we conceptually develop the potential role of forest bio-hubs. We then compare current bio-hub development in three U.S. regions—the Pacific Northwest, the southwest region, and the southeastern U.S. We use a “SWOT” framework to compare strengths, weaknesses, opportunities, and threats for each region. We consider transportation distances, topography, proximity to markets, harvesting methods, and wood products development. Innovation and adaptability would play key roles in forest bio-hub development, especially with dynamic conditions related to markets, wildfire risks, biomass utilization policy, and community socioeconomic factors.

Carbon Footprint and Feedstock Quality of a Real Biomass Power Plant Fed with Forestry and Agricultural Residues

Phasing out fossil fuels to renewables is currently a global priority due to the climate change threat. Advocacy for biomass use as an energy source requires assessing the quality biomass and ecological impacts of bioenergy supply chains. This study evaluated the quality of biomass residues from orchards and silviculture transported from different Northern and Central Italy locations and the carbon footprint of a biomass power plant. The total greenhouse emissions were calculated based on primary data for 2017 according to the ISO/TS 14067. All the residue samples showed their suitability for biofuel use. Ash content was relatively low on average (3–5% d.m.), except for grapevine residues (18% d.m.). The lower heating value was within the expected range of 15–21 MJ kg−1 for plant species. The average GHG emission from the power plant was 17.4 g CO2 eq./MJ of electrical energy, with the energy conversion (38%) and transportation of biomass (34%) phases being the main impact contributors. For this study, impacts of residual agricultural residue were about half that of residues from forest management, mainly due to chipping and greater transport distance. Results show that sourcing residual biomass materials for electricity generation close to power plants significantly reduce GHG emissions compared to conventional fossil fuels.